Device for bending profiles by thinning a wall of the profile

ABSTRACT

In a device and in a process for bending a tube  72 , the tube  72  is guided through a bending tool  71 , which rotates around a section guide housing  81, 82  and also around a cam unit formed by two tubes  83, 84 . Rollers  86  serve as pressing elements, and a mandrel  73  serves as an abutment; as the tube  72  is pushed through the section guide housing  81, 82  between the rollers  86  and the mandrel  73 , it is squeezed to different degrees in different areas of its wall cross section, so that, as a result of the stretching and squeezing of the tube  72 , a bend is produced. The size of the bending radius of the tube  72  to be bent is determined by the eccentricity adjusted via the cam unit and/or by the axial feed of the rollers  86  toward the section guide housing  81, 82 . By means of the bending tool  71  according to the invention, it is possible to produce different bending radii in one and the same bending device in a tube  72  to be bent by changing the feed, that is, the distance between the rollers  86  and the mandrel  73 . No uncontrolled cracks or deformations occur. The bending tool  71  used imposes only minimal limitations on how the tube  72  can be bent in any of 3 dimensions, which means that a section can be bent into any desired shape.

This application is a 371 of PCT/EP02/05523, filed May 18, 2002.

The invention pertains to a device and to a process for bending sectionswhich have a section wall with cross-sectional areas at differentdistances from the axis of the bend to be produced, comprising a bendingtool with at least one pressing element assigned to the outside surfaceof the section wall, the bending tool also having at least one opposingpressing element assigned to at least one of the pressing elements, andwhere at least one pressing element and at least one opposing pressingelement assigned to one of the pressing elements can be moved relativeto each other to squeeze at least one cross-sectional area of thesection wall in the cross-sectional direction, this cross-sectional areabeing on the outside with respect to the axis of the bend.

A bending device of this type is also described in DE 689 018.

Various devices are known which can be used to bend sections; in thesedevices, a force greater than the yield point of the material isintroduced into the workpiece. This force has the effect of stretchingpart of the outside surface of the workpiece and of compressing part ofthe inside surface, thus producing a bend. Certain limits are imposed onthis bending process by the shape-holding strength of the material,because, when the shape-holding strength is exceeded, the material cancrack, become indented, or buckle. At the same time, the number ofdegrees of freedom is limited. Machines which apply this processespecially to tubing are known as mandrel bending machines, bendingpresses, and multi-roll bending machines. The radii of the bends whichcan be produced by mandrel bending machines and bending presses arepredetermined by the shapes of the tools. Multi-roll machines make itpossible to produce different radii, which follow each other in helicalfashion, but only relatively large ratios between the radius and thediameter of the tubing (5–10) are possible.

In the case of roll-stretch bending or round bending, theformer-dependent shape is produced by the rotation of a center roll,while bending moment is exerted simultaneously by pressing the sectionagainst the center roll. In the case of roll-stretch bending, anadditional axial tensile stress is superimposed on the other stresses.

A bending machine is known from DE 689 018, in which a tool cooperatingwith an impact-producing object (e.g., an air hammer) is used to producecurves by striking sectioned rails. Two or more movable hammers areassigned to an anvil; the hammers are controlled by the impact-producingdevice. As a result of their shape and the distance between them and theanvil, which is itself designed in a manner corresponding to the e ofthe rail, the hammers act on the two adjoining sidepieces of the railsection in such a way that the rail is stretched in a way so as toobtain the desired curvature.

The present invention is based on the task of creating a bending deviceand a bending process which do not need to exert any axial tensilestresses during the bending of sections and which allow bends of anydesired shape to be produced.

This task is accomplished with respect to the device in that thepressing element or elements are advanced toward the opposing pressingelement or elements in the cross-sectional direction while maintaining agap between them, the width of the gap in at least one cross-sectionalarea being smaller than a cross-sectional area of the wall of thesection to be bent which is being transported through the gap.

The device according to the invention thus offers the advantage thatsections with different radii of curvature can be produced in one andthe same bending device. An opposing pressing element such as a cheek, aroller, a roll, or a mandrel, which is designed to conform to thesection to be bent, is held in place against the inside walls of thesection to be bent and is positioned in such a way that it opposes apressing element, which can be moved toward the opposing pressingelement to within any selected distance. The approach of the twoelements toward each other can also be accomplished by advancing theopposing pressing element toward the pressing element in such a way thata gap always remains between the pressing element and the opposingpressing element, through which the section to be bent is transported.As it is being transported through the gap, the section or a part of thesection is squeezed powerfully enough to produce the desired bend. As aresult of this squeezing effect, the sectioned wall becomes thinnerwhere it was squeezed, either at just one point or possibly over acertain longitudinal extent of the section. On the part of the sectionopposite the squeezed part, the section can be compressed. During abending operation, the section to be bent can also be rotated, so thatthe direction in which the section is bent can also be influenced.

According to the invention, the section provided for bending is squeezedto varying degrees by the exertion of radially oriented forces onvarious cross-sectional areas of the section wall, so that the bendingis caused by the stretching and squeezing of the material of thesection. The force can be applied by a ram, by a roll, or by a rolleracting against an opposing pressing element resting against the section,and the material of the section can be squeezed to a predeterminedextent between the ram, the roll, or the roller and the opposingpressing element to various degrees around the circumference or contourof the section. During a bending process, the section to be bent can, asneeded, be pushed either in stages or continuously in the axialdirection of the section through the bending device according to theinvention, that is, intermittently in shorter or longer steps orcontinuously at uniform or at varying speed.

According to the process implemented in accordance with the invention,the wall forming the outside dimension of the section is squeezedbetween two tools, portion by portion, by the advance of the workpiece(section) to be bent. Thus the stretching required to produce the bendis produced by the squeezing of the wall on one side of the workpiece.The material is squeezed in the radial direction, which thus causes astretching in the axial direction. The section is thus bent. On theopposite side of, for example, the wall of tube, it is also possible forsqueezing in the axial direction of the section to occur. In thisprocess, the degree of bending can be adjusted quite accurately byvarying the amount of force exerted; in comparison with the state of theart, no blows need to be struck, and the danger of overstretching isavoided. The pressing elements and the opposing pressing elements areset as close to each other as desired, and the desired bend can beobtained by adjusting the cross section of the gap to the desired width.During a bending operation, the pressing element or elements and theopposing pressing element or elements can be moved in the radialdirection in such a way that the size of the gap and/or the shape of thegap changes. As a result, the surface of the material will also have abetter appearance, and no additional tools such as wrinkle smoothers arerequired to obtain a surface of acceptable appearance. Any desired bendcan be produced by rotating the section to be bent and then by squeezingit. It is also easy to influence the bending, that is, the degree ofbending or the bending direction, by adjusting the feed and thus thelength of the individual sections. The feed can be either intermittentor continuous. Sections with high-quality surfaces are obtained when theforce is introduced transversely by way of an upper and/or a lower roll.So that the section can be given any desired shape, various bends can beachieved by varying, according to a preferred embodiment, the amount offorce introduced by way of the roll surface. By squeezing only one sideof the section, such as the top, only one edge part of the material issqueezed, and thus the change in length occurs only in this area, whichmakes it possible to obtain a section with the desired curvature.

A mandrel is inserted into the section to be bent, such as a length oftubing, and the material is then squeezed between the mandrel and a ram.The ram is designed here so that it conforms to the external shape ofthe section to be bent and is thus able to transmit the forceeffectively. In the case of a continuous bend, the force can also beintroduced by a roller or by a ram, which exerts a varying amount offorce. The opposing pressing element is a mandrel, which is insertedinto the interior of the section and rests at least partially againstthe inside surface of the section; this mandrel absorbs the pressure ofthe movable ram or roller.

A similarly designed device, by means of which the process can beimplemented, has a die for guiding the material to be bent, where a tool(pressing element), which introduces the force, such as a ram, is ableto move laterally along the die toward the workpiece. The die also hasan abutment for the ram at the bottom end. A mandrel, which can beinserted into the workpiece, is also provided, against which the ram canbe moved (predetermined setting), so that the workpiece material issqueezed between the mandrel and the ram, which causes the material tostretch out in the axial direction.

A device for bending sections has at least one roller or roll instead ofa ram as a force-exerting tool. The amount of force exerted along thesurface of the roll can be varied.

In various preferred embodiments of the bending device according to theinvention, the minimum of one pressing element is designed as a movableram or as movable rams and/or as a movable roll or as movable rollers,and the opposing pressing element is designed as a mandrel, which isinstalled opposite the ram or rams or opposite the roller or rollers,and which can be positioned to rest against at least part of the insidecircumferential surface of the hollow section.

According to the invention, the size and/or the cross-sectional shape ofthe gap is adjustable. By advancing the one or more pressing elementstoward the one or more opposing pressing elements, gaps of any desiredshape and size can be obtained, in which the sections of the sectionwalls being transported through the gap can be squeezed in any desiredway. Bending radii can be produced over a wide range, and a wide varietyof bending shapes can be obtained.

The section to be bent can be pushed and/or pulled through the gap. Thishas the advantage that, depending on the size of the section, on thethickness of the material of the section to be bent, and/or on thecontour of the section, it is possible to select from among a widevariety of transport modes to guide the section to be bent between thepressing elements and the opposing pressing elements. It is obvious thatthe bending tool (pressing and opposing pressing elements) can also bemoved with respect to the section to be bent, i.e., moved in the axialdirection, in order to bend the selected section in the desired way.

The pressing elements can be designed as rams, as rollers, and/or asrolls, whereas the opposing pressing elements can be in the form ofmandrels, support cheeks, anvil configurations, rollers, rolls, etc. Theopposing pressing elements rest against the interior areas of the crosssection of the section wall to be bent, and it is obvious that theexternal contours of the pressing elements and of the opposing pressingelements will be adapted to conform to the shape of the section to bebent.

As a further elaboration of the bending device according to theinvention, one or more rollers are rotatably supported so that they areparallel to the axial course of the section to be bent or so that theaxis of rotation of the rollers is transverse to the axial orientationof the section to be bent.

The pressure exerted on the ram or rams or on the one or more rollerscan be varied in the direction transverse to the axial orientation ofthe section to be bent. Varying the pressure setting in this way makesit possible to bend the section to be bent in different directions.

In addition, the direction in which a section is bent can be influencedby using holding means such as a chuck to hold the section during thebending operation, so that the section can either be kept stationary inthe bending direction, shifted axially, and/or rotated around the axisof the section.

In a preferred embodiment of the bending device according to theinvention, the bending device has a stationary section guide housing. Acam unit is mounted so that it can rotate around the section guidehousing, and the pressing element or elements are mounted on the camunit so that they can rotate independently of it.

The orientation of the pressing element or elements with respect to thesection guide housing can be adjusted independently of the cam unit. Thecam unit can be formed by a first and a second circular tube, one ofwhich, when seen in cross section, surrounds the other. The two tubescan be rotated relative to each other. In one embodiment, the circulartubes can be locked in place in any rotational position.

In another embodiment of the bending device according to the invention,the orientations of the pressing element or elements with respect to thesection guide housing can be adjusted by means of one or more wedge rodsor by one or more conical sleeves.

When the pressing elements are mounted so that they can rotate aroundthe section guide housing, the material can be squeezed relativelyuniformly around the entire circumference of the section.

It is also advantageous for the cam unit to be adjustable either by ahydraulic system or by means of a gear assembly.

With respect to the process according to the invention for bendingsections, the task is accomplished by bending the sections by exertingforce on both sides, in the cross-sectional direction, of across-sectional area of the wall of the section situated on the outsidewith respect to the axis of the bend, as a result of which this area issqueezed and thus stretched out in the longitudinal direction of thesection; and by not exerting any force in the cross-sectional directionon a cross-sectional area of the wall of the section situated on theinside relative to the axis of the bend or by exerting force on bothsides of this inside area to squeeze it and thus to stretch it out inthe longitudinal direction of the section but to a lesser degree thanthe cross-sectional wall area on the outside. These are the processsteps that are used to bend sections with walls with cross-sectionalareas that are at different distances from the axis of the bend. Atleast one section of the wall of the section or sections to be bent istransported through a gap, which brings about the squeezing.

In additional embodiments of the process, one or more cross-sectionalareas of the section wall are acted upon and squeezed by one or moremovable rams or by one or more rotating rollers, which are moved via acam unit and/or via feed devices to positions at a greater or lesserdistance away from the longitudinal axis of the hollow section to bebent.

The device according to the invention and the process according to theinvention make it possible to bend sections of any desiredcross-sectional shape, including sections which are closed all the wayaround the circumference, such as circular tubing, into shapes which canhave almost any radius of curvature and which can proceed in almost anydirection, with a high degree of dimensional accuracy andreproducibility. Cracks and uncontrolled deformations of the sections tobe bent are avoided. The bending tools impose only minimal limitationson the three-dimensional possibilities for bending a section, whichmeans that any desired shape can be produced by the action of one andthe same bending device on the section to be bent.

In addition, the previously mentioned features and those presented belowcan be used either individually or in any desired combination with eachother. The previously mentioned embodiments are not to be understood asa final list; rather, they are to be understood merely as examples.

The individual figures of the drawing show both the functionalprinciples and an embodiment of the bending device according to theinvention in highly schematic form. The individual features shown in thedrawings are not to scale. The features of the bending device accordingto the invention are presented in such a way that their inventive designcan be easily appreciated:

FIG. 1 shows a longitudinal cross section of the bending principle of abending device according to the invention;

FIG. 2 shows a cross section along line II—II of FIG. 1;

FIG. 3 shows a longitudinal cross section of the principle of a bendingdevice according to the invention with pressing elements in the form ofrollers;

FIG. 4 shows a cross section along line IV—IV of FIG. 3;

FIG. 5 shows a longitudinal cross section of a bending principleaccording to the invention with rollers as the pressing elements andwith a mandrel as the opposing pressing element;

FIG. 6 shows a view along line VI—VI of FIG. 5;

FIG. 7 shows a side view of a bending principle according to theinvention with an H-shaped section for bending;

FIG. 8 shows a view along line VIII—VIII of FIG. 7;

FIG. 9 shows a side view of a bending principle according to theinvention with rollers/rolls as pressing and opposing pressing elements;

FIG. 10 shows a view along line X—X of FIG. 9;

FIG. 11 shows a front view of a bending principle according to theinvention with a U-shaped section for bending;

FIG. 12 shows a side view of an embodiment of a bending device accordingto the invention;

FIG. 13 shows a longitudinal section through a bending tool of thebending device of FIG. 12;

FIG. 14 shows a detailed view of the pressing elements of a bendingdevice according to the invention in longitudinal cross section;

FIG. 15 shows a view along line XV—XV of FIG. 14;

FIG. 16 shows a detailed view of the pressing elements of a bendingdevice according to the invention with conical sleeves;

FIG. 17 shows a view along line XVII—XVII of FIG. 16;

FIG. 18 shows another cross section through a bending tool of a bendingdevice according to the invention in the area of the pressing elements;

FIG. 19 a shows a schematic diagram of a cam unit of a bending deviceaccording to the invention in the neutral position; and

FIG. 19 b shows a schematic diagram of a cam unit of a bending deviceaccording to the invention in which the maximum degree of eccentricityis being used.

FIG. 1 shows a bending principle 10 for a bending device according tothe invention with a die 11, through which a circular tube 12 can bepushed. The die 11 holds the tube 12 and maintains it in its properorientation. The die 11 is stationary. In the tube, a mandrel 13 isinserted, which rests against the inside circumference of the tube 12;the diameter of the mandrel is as large as the inside diameter of thetube 12. The mandrel 13 is permanently connected to a mandrel rod 14, bywhich the mandrel 13 is positioned and held immovably in the tube 12during the bending process. The tube 12 can be pushed in the directionof the arrow 15 through the die 11 and over the mandrel 13. A ram 17,which is free to move in the direction of the arrow 16, is mounted atthe end of the die 11, so that, when the ram exerts pressure on the tube12, it will also be pressing against the mandrel 13, which forms anabutment to cooperate with the ram 17. In the embodiment according toFIG. 1, the ram 17 extends around half of the circumference of the tube.The ram 17 can be pushed with such force against the externalcircumferential surface of the tube that the tube 12 is squeezed in thearea of the ram 17 and thus stretched out. As a result, a bend isproduced in the tube 12. It is obvious that the tube 12 can be squeezedby several movable rams mounted around the circumference of the tube 12.If the tube 12 does not have a circular cross section, movable ramswhich cover different areas of the outside circumference of the tube canbe used, and the cross-sectional form of the mandrel will also always bedesigned to conform to the inside circumference of the tube to be bent,so that the mandrel can serve as an effective abutment for the movablerams.

The tube in FIG. 1, into the interior of which an axially movablemandrel 13 has been inserted, is subjected to a squeezing force actingin the radial direction; the squeezing between the movable ram 17 andthe mandrel 13 leads to a stretching in the axial direction of the tubewall. The die 11 serves as a guide and as an abutment underneath the ram17 to absorb the force applied by the ram 17. By means of the axial,stepwise feed of the tube 12, the tube 12 can be bent into the desiredform. If desired, it is also possible to use a wrinkle smoother here.The desired degree of bending is obtained by adjusting the amount offorce exerted.

FIG. 2 shows the arrangement of the bending principle 10 of FIG. 1 in aview along line II—II. The tube 12 is held stably in the die 11, and themandrel, which completely fills the free inside diameter of the tube,maintains the diametric shape of the tube 12 even when the ram 17 ispressed in the directions of arrow 16 with such force against theoutside circumference of the tube 12 that the tube 12 is squeezed in thearea of contact between the ram 17 and the outside circumference of thetube. The ram 17 surrounds essentially only half of the circumference ofthe tube 12, and across this area the ram produces a squeezing effect inthe radial direction and a stretching of the tube 12 in the axialdirection. The circumferential surface of the tube 12 to be bentsituated opposite the ram 12 rests in the die 11.

FIG. 3 shows another embodiment of a bending principle 20 according tothe invention. A die 21 guides a circular tube to be bent in such a waythat its axis remains stable even when force is exerted on the tube. Amandrel 23, which is kept stationary by a mandrel rod 24, is insertedinto the tube 22 and ensures that, even when force is being exerted onthe outside circumference of the tube 22, the original diameter or shapeof the tube will not be changed.

The circular tube 22 can be pushed continuously in the direction ofarrow 25 through the die 21 so that tube 22 will be bent. Rollers 27,which conform to the external contour of the tube 22, rotate in thedirection of arrow 26 on the outside circumference of the tube 22. Thepressures which the rollers 27 exert on the outside circumference of thetube 22 can be varied over their surfaces 28, and therefore the circulartube 22 can be bent as it is being squeezed.

FIG. 4 shows the bending principle according to FIG. 3 in a view alongline IV—IV. The shape of the tube 22 is maintained by the mandrel 23,and the rollers 27 exert different forces via their roller surfaces 28on the outside circumference of the tube 22, so that the tube 22 can bebent in the desired manner. The rollers 27 can be advanced toward eachother to different degrees and can rotate in the direction of the arrows26 in whatever orientation they have assumed. In FIG. 4, the axis ofrotation of the rollers 27 is shown in broken line. It is also possiblefor the axis of rotation of the rollers 27 to be tilted out of theposition shown in the figure, so that the force exerted by the roller onthe hollow section to squeeze it can be varied across the surface of theroller.

FIG. 5 shows a bending principle 30 according to the invention with astationary die 31 and a tube 32 with a round cross section, which isguided through the die 31. A mandrel 33 is inserted into the tube 32;the mandrel is pushed by a mandrel rod 34 into a position suitable forthe bending of the tube 32. The tube 32 to be bent passes through thedie 31 in the direction of the arrow 35, and the rollers 37, which serveas pressing elements, are advanced in the direction of the arrow 36toward the outside wall of the tube in such a way that, as the tube 32is pushed through the die 31 while the mandrel 33 is being held inposition, the outside circumferential surface of the tube 32 issqueezed. The rollers 37 are mounted on a roller holder 38, which canrotate around the tube 32 to be bent.

FIG. 6 shows a view along line VI—VI of FIG. 5; in the drawing, therollers 37 are covered by the roller holder 38. In the interior of thetube 32, the mandrel 33 is arranged in such a way that it fills up theentire hollow space inside the tube 32 and can thus form an effectiveabutment and opposing pressing element for the pressing elements, which,in the present case, are the rollers 37. The rollers 37 are advancedtoward the mandrel 33 in the direction of the arrow 36 until there isonly a small gap between the mandrel 33 and the rollers 37, which gapproduces the desired squeezing and thus the desired bending when thetube 32 is pushed through the gap.

FIG. 7 shows a side view of another bending principle 40 according tothe invention. An H-shaped section 42 is guided with freedom of movementthrough a die 41, and cheeks 43 are brought up from both sides to restagainst the lateral inside walls and the web of the H-shaped section 42to be bent; according to the invention, these cheeks form the opposingpressing elements. The H-section 42 to be bent is conducted through thedie 41 in the direction of the arrow 45, and as the rollers 47 areadvanced in the direction of arrow 46, the outside surfaces of theH-section 42 to be bent are squeezed. To produce the squeezing shown inthe figure, the upper roller 47 is advanced closer to the cheeks 43 thanthe lower roller 47. No change in the feed setting is made during thebending operation.

FIG. 8 shows a view along line VIII—VIII of FIG. 7. The direction inwhich the H-section 42 to be bent proceeds through the bending device isoutward from the plane of the drawing. The cheeks 43 stabilize theH-section 42 to be bent on both sides, and the bending of the H-section42 is produced by the rollers 47, which can be also be designed asrolls. The arrows 46 indicate the forward feed of the rollers 47 towardthe cheeks 43.

FIGS. 7 and 8 show the bending principle on the basis of an H-shapedsection 42, where an upper roller 47 serves as the force-introducingtool and the lower roller 47 as the abutment and/or also as aforce-exerting tool. The H-section 42 is guided by the cheeks 43, whichalso form abutments for the rollers 47. As can be seen more clearly inFIG. 8, cheeks 43 are provided on the sides of the H-section 42. Thematerial is squeezed between these cheeks and the rollers 47. The forcerequired to squeeze the H-section 42 is exerted by way of the rollers47; the force being exerted can be varied over the surface of theroller. If the force being exerted on the H-section 42 varies over thesurface of the roller, it is possible to obtain a lateral curvatureproceeding out from the plane of the drawing of FIG. 7. A curvature ofthe H-section 42 to be bent as shown in FIG. 7 occurs when the forcesare exerted uniformly across the surfaces of the rollers 47 onto theH-section 42.

FIG. 9 shows a side view of another bending principle 50 according tothe invention with an H-shaped section 52 to be bent. Rollers/rolls 53are used as the opposing pressing elements, and the H-section 52 to bebent is transported in the direction of the arrow 55 during the bendingoperation. The arrows 56 indicate the feed of the pressing elements,which are rollers/rolls 57 here; this feed presses the rolls 57 againstthe outside surface of the H-section 52 to be bent. During the processof bending the H-section 52, both the rolls 53 and the rolls 57 rotate.The arrows 56′ indicate the feed direction of the rolls 53 (opposingpressing elements) toward the inside walls of the H-section 52.

FIG. 10 shows a view along line X—X of FIG. 9, in which the H-section tobe bent is brought out from the plane of the drawing as it passesthrough the bending process. The rolls 57 press in the direction of thearrows 56 against the outside surfaces of the H-section 52 to be bent,and the rolls 53 form the opposing pressing elements and can also bepressed to varying degrees in the direction of the arrows 56′ againstthe inside walls of the H-section 52 to be bent. The bending principle50 according to FIGS. 9 and 10 is especially advantageous for processesworking with continuous feed because of the reduced wear attributable tothe use of rollers for bending. It is obvious that it is not necessaryto use four rolls 53 as opposing pressing elements; in the case ofsimpler H-sections 52 with thinner walls, bending is also possible evenwhen only one roll 57 is used for the bending operation.

FIG. 11 shows a bending principle 60 according to the invention for aU-shaped section 52 to be bent, in which a roll 63 or an anvil is usedas the opposing pressing element. To bend the U-section 62, theU-section 62 to be bent passes over the roll 63 or over the anvil,outward from the plane of the drawing, for example, and by advancing therolls 67 or rollers in the direction of the arrow 66, the U-section 62can be bent in the desired manner. The rolls 67 can be subjected tovarying pressures across their surfaces, so that a wide variety ofbending shapes can be obtained by the use of the bending principle 60according to the invention.

FIG. 12 shows a side view of a bending device 70 according to theinvention with a bending tool 71 for bending circular tubes 72. Amandrel has been pushed longitudinally into the circular tube 72; therod 74 of the mandrel can be fixed in any desired position on thebending device 70. The tube 72 can be pushed through the bending device71 in the direction of the arrow 75. By means of a drive belt 76, whichis connected to a rotating drive motor 77 for the bending tool 71, thebending tool 71 can be rotated around the circular tube 72. An adjustingdevice for a cam unit of the bending device 70 is indicated at 78; thisunit can shift the axis of rotation of the bending tool 71 away from thelongitudinal axis of the circular tube 72. In the neutral position ofthe bending device 70, the axis of rotation of the bending tool 71coincides with the longitudinal axis of the tube 72 to be bent. When theaxis of rotation is shifted away from the longitudinal axis of the tube72, the pressure which the bending tool 71 exerts on the variouscross-sectional areas of the wall of the tube 72 to be bent varies. Byway of a clamping chuck 79, the tube 72 to be bent is held in positionin the bending device 70, and a tube feed unit 80 pushes the tube 72 tobe bent through the bending tool 71. The chuck 79 can also be rotated ifdesired, so that the tube 72 to be bent can be bent in differentdirections, depending on how the tube 72 is rotated by the chuck 79.

FIG. 13 shows a cross section of a part of the bending device accordingto the invention with the bending tool 71. The tube 72 to be bent passesthrough a section guide housing 81, 82, in which the tube 72 to be bentcan be moved in a positionally stable manner. In the interior, the tube72 to be bent is stabilized by a mandrel 73, which is kept in thedesired position by the mandrel rod 74 during the bending process. A camunit is mounted on the stationary section guide housing 81, 82; this camunit can be rotated with respect to the section guide housing 81, 82.The cam unit is formed by a first and a second tube 83, 84, each ofwhich has different wall thicknesses around their circumferences. Thetubes 83, 84 can be rotated to a greater or lesser degree with respectto each other, so that the bending tool 71 supported rotatably on thecam unit can be pushed to a greater or lesser degree away from thelongitudinal axis of the tube 72. When the tubes 83, 84 are rotated withrespect to each other, the axes of the cam unit and of the circular tube72 to be bent no longer coincide, and the bending tool 71 rotatablysupported on the cam unit rotates eccentrically around the longitudinalaxis of the tube 72 to be bent. The support of the bending tool 71 onthe second tube 84 of the cam unit is indicated by the reference number85 in the figure.

The bending tool 71, which, during a bending process, rotates around thecam unit, consisting of the first and the second tube 83, 84, hasrollers 86 to serve as pressing elements, which are rotatably supportedon axles 87. The rollers 86 press via their surfaces 88 against theoutside circumference of the tube 72 to be bent. As the bending tool 71rotates around the tube 72 to be bent, the rollers 86 thus squeezedifferent cross-sectional areas of the wall of the tube 72 to be bent todifferent degrees, so that these varying forces have the effect ofbending the tube 72. The tube 72 to be bent is stretched or squeezed tovarying degrees in different cross-sectional areas of its wall.

Independently of the cam unit, which is formed by the first and thesecond tube 83, 84, the rollers 86 can also be pushed by one or morewedge rods 89 toward the tube 72 to be bent. The rollers 86 aresupported in a roller housing 90, which is supported so that it canslide up and down in the housing of the bending tool 71. When the wedgerods 89 are pushed in the direction of the arrow 91, the diameter of theorbit of the rollers 86 decreases, and the pressure on the circular tube72 to be bent increases. The pressure which the rollers 86 exert on theoutside circumferential surface of the circular tube 72 to be bent canalso be reduced by retracting the wedge rods 89 in the directionopposite that of the arrow 91.

The bending device shown in FIG. 12 makes it possible to adjust thevarious forces, acting on a circular tube 72, to be bent independentlyof each other both by shifting the cam unit in the desired manner andalso by adjusting the rollers 86 with respect to each other.

FIG. 14 shows a simplified cross-sectional diagram, which illustratesagain how the rollers 86 are adjusted by means of the wedge rods 89,which are components of the bending tool 71. The section guide housing81, 82 is indicated in the figure; it guides the tube 72 to be bentduring its passage through the bending device. The mandrel 73, held inposition by the mandrel rod 74, supports the contour of the section andalso serves as an abutment for the rollers 86, which form the pressingelements. The rollers 86 are rotatably supported in a roller housing 90,which can move up and down inside the housing of the bending tool 71 byway of the wedge rods 89. The bending tool rotates in the manner shownin FIG. 7 eccentrically around the longitudinal axis of the tube 72 tobe bent and thus squeezes the upper area of the tube 72 to be bent morestrongly than the lower area. This is indicated by the thinning of thecross section of the wall of the section in FIG. 14. The tube 72 to bebent is pushed through the bending device in the direction of the arrow75.

FIG. 15 shows a view along line XV—XV of FIG. 14. The interior of thetube 72 to be bent is filled by the mandrel 73, and rollers 86 exertpressure on the outside circumference of the tube 72. The rollers 86 arerotatably supported on axles 87, which are mounted in the roller housing90. The roller housing 90 can be shifted via wedge rods 89. The bendingtool can rotate in the direction of the arrow 92 around the tube 72 tobe bent. The components in FIG. 15 not described in detail are parts ofthe bending tool 71, which hold together and support the individualpressing elements, here the rollers 86.

FIG. 16 shows another embodiment of a bending tool 100, which can beused in a bending device according to the invention. A section guidehousing 101 stably guides a tube 102 to be bent through the bendingdevice according to the invention, and a mandrel 103 supports andsecures the cross-sectional form of the tube 102 to be bent. The mandrel103 is held by a mandrel rod 104, and the tube 102 to be bent, by way ofthe mandrel 103 and by way of the mandrel rod 104, can be pushed throughthe section guide housing 101 in the direction of the arrow 105. Rollers106 are provided as pressing elements, and the mandrel 103 serves as theabutment. By moving the conical sleeves 107 toward each other, thedistance between the rollers 106 can be adjusted, and by means of thisadjustment, the pressure on the outside circumferential surface of atube 102 to be bent can be increased or decreased. The rollers 106,which are rotatably supported in a cage, are driven via the rotation ofthe conical sleeves 107 by static friction.

FIG. 17 shows a view along line XVII—XVII of FIG. 16. The interior ofthe tube 102 to be bent is completely filled by the mandrel 103, and thetube 102 to be bent is squeezed against the mandrel 103 by the rollers106, as the bending tool rotates around the tube 102 to be bent in oneof the directions of the arrow 108. The conical rings 107 make itpossible to shift the rollers 106 to varying degrees, which arerotatably supported in a cage, toward the outside circumference of thetube 102 to be bent.

FIG. 18 shows a different cross section through a bending tool which canalso be used in the bending device according to the invention. A tube112 to be bent is stabilized by a mandrel 113, which simultaneouslyforms an abutment for the pressing elements. Rollers 116 are rotatablysupported in roller housings 115, and as they rotate in one of thedirections of the arrow 118, they squeeze the tube 112 to be bent tovarying degrees around the circumference of the tube 112, so that, aftera bending operation, the tube 112 to be bent has wall cross sections ofdifferent thicknesses in the bent area. By way of wedge rods 119, theroller housings 115 can be shifted up and down inside the housing of thebending tool.

It is obvious that the axial feeds shown in FIGS. 13–17 with respect tothe tube to be bent can also be influenced by a cam unit, which cancause the bending tool rotating around the tube to be bent, to rotateeccentrically around the longitudinal axis of the tube to bent.

FIG. 19 a shows in highly schematic form the design of a cam unit 125,which can be used in a bending device of the type according to theinvention. The cam unit 125 is formed by two tubes 126, 127, which areeccentric in cross section. The two tubes can rotate relative to eachother and can be locked in any desired rotational position. In FIG. 19a, the two tubes 126, 127 are shown in a null position; that is, thetotal wall thickness, seen in cross section, is constant around theentire circumference of the cam unit 125. This means that a bendingdevice rotating around a circular orbit 129 rotates in a null positionwith an axis of rotation that coincides with the longitudinal axis ofthe tube to be bent.

FIG. 19 b shows an extreme position of the cam unit 125. The tubes 126,127 have been turned to the maximum degree with respect to each other,based on their individual eccentricities. This means that, when abending tool rotates around the circular orbit 129 around the cam unit125, the bending tool will be pressed against the outsidecircumferential surface of the tube to be bent to the maximum amount atthe uppermost point of the circular orbit, whereas the pressing elementswill be at the maximum distance away from the outside circumferentialsurface of the tube to be bent (weakest contact pressure) at the lowpoint of the orbit 129.

In a device and in a component for bending a tube 72, the tube 72 isguided through a bending tool 71, which rotates around a section guidehousing 81, 82 and around a cam unit, formed by two tubes 83, 84.Rollers 86 serve as pressing elements, and a mandrel 73 serves as anabutment. As the tube 72 is pushed through the section guide housing 81,82, it is squeezed between the rollers 86 and the mandrel 73 to varyingdegrees in different cross-sectional areas of its walls, so that a bendis produced by the stretching and squeezing of the tube 72. The size ofthe bending radius of a tube 72 to be bent is determined by theeccentricity set by way of the cam unit and/or the axial feed of therollers 86 toward the section guide housing 81, 82. By means of thebending tool 71 according to the invention, different bending radii canbe produced in one and the same bending device on a tube 72 to be bentby changing the feed, that is, the distance between the rollers 86 andthe mandrel 73. No uncontrolled cracks or deformations occur. Thebending tool 71 used imposes only minimal limitations on how a tube 72,can be bent in any of 3 dimensions, which means that a section forbending can be bent into any desired shape.

1. Device for bending sections with walls which have cross-sectionalareas at different distances from the axis of the bend to be produced,the device comprising a bending tool with at least one pressing elementand at least one opposing pressing element assigned to one of thepressing elements, and where at least one pressing element and at leastone of the opposing pressing elements assigned to it can be movedrelative to each other to squeeze at least one cross-sectional area ofthe section wall situated on the outside with respect to the axis of thebend, the at least one pressing element and the at least one of theopposing pressing elements being movable in the cross-sectionaldirection of the at least one squeezed cross-sectional area of thesection wall, wherein the pressing element or elements (27; 37; 86; 106;116) are advanced toward the opposing pressing element or elements (23;33; 73; 103; 113) in the cross-sectional direction while maintaining agap between them, the width of the gap in at least one cross-sectionalarea being smaller than a cross-sectional area of the wall of thesection to be bent which is being transported through the gap, whereinthe pressing element or elements are designed as rollers, and/or asrolls (27; 37; 47; 57; 67; 86; 106; 116) which rest against an outerside of the section wall, wherein the opposing pressing element orelements are designed as mandrels (13; 23; 33; 73; 103; 113) which restagainst interior areas of the cross section of the section wall, whereinthe device for bending has a stationary section guide housing (81, 82)and a cam unit (83, 84), which rotatably surrounds the section guidehousing (81, 82), on which cam unit the roller, the roll, or the severalrollers or rolls (86), which are rotatably supported independently ofthe cam unit (83, 84), are mounted.
 2. Device according to claim 1,wherein the size and/or cross-sectional shape of the gap can be varied.3. Device according to claim 1, wherein the section is pushed and/orpulled through the gap.
 4. Device according to claim 1, wherein theroller, the roll, or the several rollers or rolls (27; 37; 86; 106; 116)are supported rotatably and extend parallel to the axial orientation ofthe section or have an axis of rotation that is transverse to the axialorientation of the section.
 5. Device according to claim 4, wherein theroller, the roll, or the several rollers or rolls (27; 37; 86; 106; 116)and/or the mandrel (23; 33; 73; 103; 113) can be subjected to variablepressures across their dimension transverse to the axial orientation ofthe section.
 6. Device according to claim 1, wherein, during a bendingoperation, the section (72) is held stationary, is shifted in the axialdirection, and/or is rotated around an axis of the section (72) byholding means such as a chuck (79).
 7. Device according to claim 1,wherein the orientation of the roller, the roll, or the several rollersor rolls (86) with respect to the section guide housing (81, 82) isadjustable independently of the cam unit (83, 84).
 8. Device accordingto claim 1, wherein the cam unit is formed by a first and a second tube(83, 84), where, seen in cross section, one of the tubes (83, 84)surrounds the other, the two tubes being rotatable relative to eachother, and where the wall thickness of the tubes (83, 84) varies aroundtheir circumference.
 9. Device according to claim 8, wherein thecircular tubes (83, 84) can be locked in any rotational position. 10.Device according to claim 5, wherein the orientation of the roller, theroll, or the several rollers or rolls (86; 106) with respect to thesection guide housing (81; 82; 101) can be adjusted by one or more wedgerods (89) or by one or more conical sleeves (107).
 11. Device accordingto claim 1, wherein the roller, the roll, or the several rollers orrolls (27; 37; 86; 106; 116) are mounted so that they can rotate aroundthe section to be bent (22; 32; 72; 102; 112).
 12. Device according toclaim 1, wherein the cam unit (83, 84) can be adjusted hydraulically,pneumatically, or by means of a mechanical gear assembly.